Question

For the numbers 115.0, 97.5, 113.2, 104.8, and 125.3, find 90% confidence interval for the mean.

Answer 1

Solution :

n = 5

= = 555.8 / 5 = 111.16 = 111.2

s = (x - )² / n - 1  

= 445.892 / 4

s = 10.6

sample size = n = 5

Degrees of freedom = df = n - 1 = 4

t _/2,df = 2.132

Margin of error = E = t_/2,df * (s /n)

= 2.132 * (10.6 / 5)

Margin of error = E =10.1

The 90% confidence interval estimate of the population mean is,

- E < < + E

111.2 - 10.1 < < 111.2 + 10.1

101.1 < < 121.3

(101.1 , 121.3)